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US 4,126,841 AGranted
Overcurrent switch
AssigneeFujitsu Limited
InventorChiaki Maeno
Life of this patent
Estimating the term…
Abstract
An overcurrent switch is described, comprising a reed switch for series connection in an electric circuit to break the flow of an overcurrent therethrough. A magnetizing element applies a magnetic field to the reed switch, and a setting device controls the magnetic field so that at least two levels of magnetic field intensity are selectively applied to the reed switch.
Claims8
In an overcurrent switch serially connected in a circuit for interrupting the flow of current therethrough when an overcurrent is detected, the switch comprising:
- a pair of electrically conductive contacts actuable to an open position by application of a magnetic field of intensity equal to or less than a predetermined drop-out level and actuable to a closed position by application of a magnetic field of intensity equal to or greater than a predetermined pull-in level;
- and
- first means for initially applying to said pair of contacts a magnetic field of intensity equal to at least said predetermined pull-in level so as to actuate said pair of contacts to said closed position, and for subsequently reducing the intensity of said applied magnetic field to an intensity intermediate between said drop-out and said pull-in levels so as to maintain said pair of contacts in said closed position;
- the improvement wherein said pair of electrically conductive contacts are selected so as to have a drop-out level which increases substantially with increasing flow of current therethrough;
- said overcurrent switch comprising second means for applying said flow of current solely and directly to said pair of contacts whereby, when said overcurrent occurs, said dropout level rises to said intermediate level and said pair of contacts is actuated to said open position so as to interrupt the flow of current therethrough.
2 more elements
In an overcurrent switch serially connected in a circuit for interrupting the flow of current therethrough when a overcurrent is detected, the switch comprising:
- a pair of electrically conductive contacts actuable to an open position by application of a magnetic field of intensity equal to or less than a predetermined drop-out level and actuable to a closed position by application of a magnetic field of intensity equal to or greater than a predetermined pull-in level;
- and
- first means for initially applying to said pair of contacts a magnetic field of intensity equal to at least said predetermined pull-in level so as to actuate said pair of contacts to said closed position, and for subsequently reducing the intensity of said applied magnetic field to an intensity intermediate between said drop-out and said pull-in levels so as to maintain said pair of contacts in said closed position;
- the improvement wherein said pair of electrically conductive contacts are selected so as to have a drop-out level which increases substantially with increasing flow of current therethrough;
- said overcurrent switch comprising second means for raising said drop-out level to said intermediate level by applying said flow of current solely and directly to said pair of contacts, whereby said pair of contacts is actuated to said open position so as to interrupt the flow of current therethrough.
2 more elements
A method of interrupting the flow of current through a circuit when an overcurrent is detected, comprising the steps of:
- (a) providing a pair of electrically conductive contacts serially connected in said circuit and actuable to an open position by application of a magnetic field of intensity equal to or less than a predetermined drop-out level and actuable to a closed position by application of a magnetic field of intensity equal to or greater than a predetermined pull-in level, said pair of electrically conductive contacts being selected so as to have a drop-out level which increases substantially with increasing flow of current therethrough;
- (b) initially applying to said pair of contacts a magnetic field of intensity equal to at least said predetermined pull-in level so as to actuate said pair of contacts to said closed position;
- (c) subsequently reducing the intensity of said applied magnetic field to an intensity intermediate between said drop-out and said pull-in levels so as to maintain the pair of contacts in said closed position;
- and
- (d) applying said flow of current solely and directly to said pair of contacts whereby, when said overcurrent occurs, said drop-out level is increased to said intermediate level and said pair of contacts is actuated to said open position so as to interrupt the flow of current therethrough.
2 more elements
A method of interrupting the flow of current through a circuit when an overcurrent is detected, comprising the steps of:
- (a) providing a pair of electrically conductive contacts serially connected in said circuit and actuable to an open position by application of a magnetic field of intensity equal to or less than a predetermined drop-out level and actuable to a closed position by application of a magnetic field of intensity equal to or greater than a predetermined pull-in level, said pair of electrically conductive contacts being selected so as to have a drop-out level which increases substantially with increasing flow of current therethrough;
- (b) initially applying to said pair of contacts a magnetic field of intensity equal to at least said predetermined pull-in level so as to actuate said pair of contacts to said closed position;
- (c) subsequently reducing the intensity of said applied magnetic field to an intensity intermediate between said drop-out and said pull-in levels so as to maintain the pair of contacts in said closed position;
- and
- (d) raising said drop-out level to said intermediate level by applying said flow of current solely and directly to said pair of contacts, whereby said pair of contacts is actuated to said open position so as to interrupt the flow of current therethrough.
2 more elements
Dependencies are inferred from the claim text.